Inverter power module lead frame with enhanced common source inductance

Abstract

A power module has upper and lower transistor dies carried by a lead frame assembly. The assembly has a positive DC paddle for the upper die and an AC paddle for the lower die. An upper plate interconnects a second side of the upper die with the AC paddle, and a lower plate interconnects a second side of the lower die with a negative power bar. Current flowing via positive and negative power bars defines a power loop creating a main magnetic flux with a first direction in a central region and a return direction outside the central region. The upper and lower plates have outer edges having respective notches to concentrate respective portions of a return magnetic flux. Each die has a gate pad connected in a gate loop, wherein the gate loops each overlap a respective concentrated return flux thereby enhancing a common source inductance for each transistor.

What is claimed is: 
     
       1. A power module comprising;
 upper and lower transistor dies; and 
 a lead frame assembly having a positive DC paddle receiving one side of the upper die and extending to a positive power bar, an AC paddle receiving a first side of the lower die and extending to an AC power bar, a negative power bar located between the paddles, an upper plate interconnecting a second side of the upper die with the AC paddle, and a lower plate interconnecting a second side of the lower die with the negative power bar; 
 wherein current flowing via the positive and negative power bars defines a power loop creating a main magnetic flux with a first direction in a central region within inner edges of the upper and lower plates and an opposing direction outside the central region; 
 wherein the upper and lower plates have respective outer edges each having a respective notch adapted to concentrate a respective portion of a return magnetic flux; and 
 wherein each die has a respective gate pad connected in a respective gate loop, wherein the gate loops each overlaps a respective concentrated return magnetic flux portion, thereby enhancing a common source inductance. 
 
     
     
       2. The power module of  claim 1  wherein the dies each include a respective emitter pad, wherein the lead frame assembly includes a respective gate pin and an emitter pin for each die, and wherein the respective gate pins and emitter pins are connected to the gate pads and emitter pads so that a gate loop current for each die flows along the respective notch. 
     
     
       3. The power module of  claim 2  wherein a bond wire connects the emitter pin for the upper die to the AC paddle. 
     
     
       4. The power module of  claim 2  wherein the negative power bar includes a lateral strip crossing the notch in the lower plate, and wherein a bond wire connects the emitter pin for the lower die to the lateral strip. 
     
     
       5. The power module of  claim 1  wherein the transistors dies are comprised of insulated gate bipolar transistors (IGBTs), and wherein the first sides are collector sides of the IGBTs. 
     
     
       6. The power module of  claim 1  further comprising at least one coldplate spanning a lateral side of the power module, wherein an eddy current loop induced in the coldplate by the main magnetic flux is offset from the gate loops. 
     
     
       7. A power converter comprising:
 a DC link with positive and negative buses configured to receive a DC supply voltage; 
 a plurality of half-bridge power modules coupled between the buses, each power module comprising:
 upper and lower transistor dies; and 
 a lead frame assembly having a positive DC paddle receiving one side of the upper die and extending to a positive power bar, an AC paddle receiving a first side of the lower die and extending to an AC power bar, a negative power bar located between the paddles, an upper plate interconnecting a second side of the upper die with the AC paddle, and a lower plate interconnecting a second side of the lower die with the negative power bar; 
 wherein current flowing via the positive and negative power bars defines a power loop creating a main magnetic flux with a first direction in a central region within inner edges of the upper and lower plates and an opposing direction outside the central region; 
 wherein the upper and lower plates have respective outer edges each having a respective notch adapted to concentrate a respective portion of a return magnetic flux; and 
 wherein each die has a respective gate pad connected in a respective gate loop, wherein the gate loops each overlaps a respective concentrated return magnetic flux portion, thereby enhancing a common source inductance. 
 
 
     
     
       8. The power converter of  claim 7  wherein the dies in each power module each include a respective emitter pad, wherein the lead frame assemblies include a respective gate pin and an emitter pin for each die, and wherein the respective gate pins and emitter pins are connected to the gate pads and emitter pads so that a gate loop current for each die flows along the respective notch. 
     
     
       9. The power converter of  claim 8  wherein a bond wire connects the emitter pin for the upper die of each power module to the respective AC paddle. 
     
     
       10. The power converter of  claim 8  wherein the negative power bar of each power module includes a lateral strip crossing the notch in the respective lower plate, and wherein a bond wire connects the respective emitter pin for the lower die to the lateral strip. 
     
     
       11. The power converter of  claim 7  wherein the transistors dies are comprised of insulated gate bipolar transistors (IGBTs), and wherein the first sides are collector sides of the IGBTs. 
     
     
       12. The power converter of  claim 7  wherein each power module further comprises at least one coldplate spanning a lateral side of the respective power module, wherein an eddy current loop induced in the coldplate by the main magnetic flux is offset from the gate loops. 
     
     
       13. An inverter power module comprising;
 upper and lower transistor dies; and 
 a lead frame assembly connecting the dies in a half-bridge and defining a power loop including upper and lower plates connected to emitter sides of the dies; 
 wherein the plates each include a perimeter notch concentrating a return flux outside the power loop; 
 wherein the frame assembly further comprises gate loops for each die coupling to a respective one of the return fluxes. 
 
     
     
       14. The power module of  claim 13  wherein the frame assembly further comprises a positive DC paddle receiving a collector side of the upper die and extending to a positive power bar, an AC paddle receiving a collector side of the lower die and extending to an AC power bar, a negative power bar located between the paddles;
 wherein the upper plate interconnects the emitter side of the upper die with the AC paddle; 
 wherein the lower plate interconnects the emitter side of the lower die with the negative power bar; and 
 wherein current flowing via the positive and negative power bars creates a main magnetic flux of the power loop within inner edges of the upper and lower plates.